Nickel-base alloy containing mo-w-al-cr-ta-zr-c-nb-b



United States Patent 3,276,866 NICKEL-BASE ALLOY CONTAINING Mo-W-Al-Cr-Ta-Zr-C-Nb-B John C. Freche, Fairview Park, and William J. Waters, Cleveland, Ohio, assignors to the United States of America as represented by the Administratpr of the National Aeronautics and Space Administration No Drawing. Filed Apr. 14, 1964, Ser. No. 360,180

3 Claims. (Cl. 75-171) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes Without the payment of any royalties thereon or therefor.

The present invention relates to an improved nickelbase alloy having an extremely high load carrying capacity at elevated temperatures. The invention is further concerned with a nickel-base alloy having good resistance to oxidation at elevated temperatures and sufficient ductility to facilitate fabrication of the alloy int-o a sheet product.

Materials presently available for high load carrying capacity at elevated temperatures around 1900 F. include some of the refractory metals, such as tungsten, tantalum, molybdenum and columbium along with their alloys which have these metals as their base. Nicke-land cobaltbase superalloys are also used for such applications.

There are major disadvantages associated with the use of the above materials for such high-temperature, highstress applications. The high melting point refractory metals have very poor oxidation resistance at high temperatures. Therefore, these materials must be protected from oxidation in air by a protective coating applied to the material. The problem of providing adherent coatings which will give uniform coverage under operating conditions in which the temperature varies with exposure time or is drastically cycled has not been solved. Examples of such operations occur in turbine engines and in the re-entry to the atmosphere of space vehicles. As a result, the refractory metals, though suitable from a strength standpoint, are inadequate in an air environment insofar as oxidation resistance is concerned. Also, because many of these metals lack ductility they are extremely diflicult to work. The lack of oxidation resistance also complicates the working of the refractory metals, and special facilities including inert gas protection are required for fabrication. Because the refractory metals have high densities they are undesirable for many applications, particularly many aerospace applications wherein weight is a major consideration.

The strongest conventional nickeland cobalt-base alloys presently available have limited ductility and are primarily cast materials. Although there are some nickeland cobalt-base alloys that are readily workable, their shortand long-time strength properties are considerably lower at temperatures above 1800 F. than the strength properties of the cast material.

It is, therefore, an object of the present invention to provide a nickel-base alloy having improved properties at elevated temperatures.

Another object of the invention is to provide an improved nickel-base alloy having superior stress-rupture properties and oxidation resistance at elevated temperatures.

A further object of the invention is to provide an improved nickel-base alloy having sufiicient ductility to enable it to be worked into thin sections and at the same time have superior strength properties.

Still another object of the invention is to provide an improved nickel-base alloy which can readily be cast without the need for closely controlled vacuum techniques and still provide exceptionally high temperature properties.

3,276,866 Patented Oct. 4, 1966 These and other objects of the invention will be apparent from the specification which follows.

The present invention is embodied in alloys having the following composition range, the amount of each alloying element being listed as a percentage by weight:

Percent Nickel From about 49.49 to about 83.048 Molybdenum From about 2 to about 6 Tungsten From about 2 to about 10 Aluminum From about 4 to about 8 Chromium From about 4 to about 8 Tantalum From about 3 to about 12 Zirconium From about .5 to about 2 Carbon From about .05 to about 1 Columbium From about .5 to about 3.5 Boron From about .002 to about .01

A preferred alloy has the following composition by weight:

The percentage of columbium was varied in the above preferred alloy composition. It was found that as the amount of columbium in the alloy was decreased the hardness decreased proportionally in a linear fashion.

This alloy was prepared with one of the simplest possible casting techniques. The alloy was melted in a refractory crucible of stabilized zirconium oxide in a high frequency induction coil. Argon gas was used as a protective cover for the material during the melting operation. During pouring, the inert gas cover was removed, and the melts were hand poured at 350 F. :50" F. into investment molds heated to 1600 F. Heats were slow cooled to room temperature before removing the castings from the molds.

The alloy may also be prepared by controlled vacuum melting techniques. This can result in further improvements in physical properties, as has been demonstrated with many commercial nickel-base alloys. Vacuum melting allows much closer alloying control, reduces the interaction of such active elements as aluminum and zirconium with oxygen, and permits the drawing off of highly volatile low-melting point tramp element constituents. Reduced gas content and improved cleanliness of the melt also can be achieved by vacuum melting.

The above alloy composition is similar to that of the alloy disclosed in copending US. patent application Serial No. 107,866, filed May 4, 1961, now Pat. No. 3,167,426. The present alloy includes columbium as an alloying constituent but contains no vanadium. This results in a major improvement in oxidation resistance as well as high temperature tensile strength. The present alloy also differs from the alloy disclosed in the aforementioned patent in that boron is added for high temperature strength.

The present alloy derives much of its strength from the formation of a fine dispersion of a complex nickelbase intermetallic compound of the Ni Al type with substantial amounts of tantalum, chromium and columbium in solution. Complex tantalum-columbium carbides are also present in the alloy of the present invention and serve as additional strengtheners.

The alloy of the present invention compares favorably in high temperature tensile strength, oxidation resistance 4 TABLE 111 Oxidation resistance as measured by weight loss,

Inga/cm.

Time, hr. Temperature TABLE I Nominal chemical compositions W Cb Al Rene 4L-.- Alloy 1 New Alloy.

COUOO! The improve-d high temperature strength of the alloy made in accordance with the present invention is shown in Table 11 wherein the ultimate tensile strength of the cast New Alloy is compared with those of two commercially-available cast alloys as well as that of the cast nickel-base alloy disclosed in Pat. No. 3,167,426 at 1900 F. Table II also shows the ultimate tensile strength of the New Alloy sheet at 1800 F. together with that of a commercially-available sheet at the same high temperature. The ultimate strength at 1900 F. of a commercially-available powder product is listed in Table II for comparison purposes.

The improved oxidation resistance of the New Alloy at high temperatures is shown in Table III. The oxidation resistance at 1900 F. is listed for the alloy made in accordance with the present invention, three commercially-available alloys, and the alloy disclosed in the copending application.

It is apparent from the above tables that the nickelbase alloy of the present invention has improved properties at elevated temperatures which make the alloy useful for a number of different applications. For. example, this alloy can be utilized in turbojet engines as a turbine bucket or stator vane material, as a high temperature structural member for aerospace vehicles,

and as a sheet material for surface panels of re-entry' vehicles.

Although the present invention has been described in conjunction with a preferred embodiment, it is to 'be understood that modifications and variations. may be resorted to without departing from the spirit of the, invention or the scope of the subjoining claims.

What is claimed is:

1. A nickel-base alloy consisting essentially of from 49.49% to 83.048% nickel, from 2% to 6% molybdenum, from 2% to 10% tungsten, from 4% to 8% aluminum, from 4% to 8% chromium, from 3% to 12% tantalum, from 0.5% to 2% zirconium, from .05% to 1% carbon, from .5% to 3.5% columbium, and from .002%

to .01% boron.

2. A nickel-base alloy consisting essentially of 4% molybdenum, 4% tungsten, 6% aluminum, 6% chromium, 8% tantalum, 1% zirconium, .125%' carbon, .003 boron, from .5 to 3.5 columbium, and the balance nickel.

3. A nickel-base alloy as claimed in claim 2 including 2.5% colunibium.

References Cited by the Examiner UNITED STATES PATENTS 2,994,605 8/1961 Gill et al -171 3,122,433 2/ 1964 Greenewald 75171 3,166,413 1/1965 Shaw et a1. 75-171 3,167,426 1/1965 Frecke et al. 7517l DAVID L. RECK, Primary Examiner.

-R. O. DEAN, Assistant Examiner, 

1. A NICKEL-BASE ALLOY CONSISTING ESSENTIALLY OF FROM 49,49% TO 83.048% NICKEL, FROM 2% TO &% MOLYBDENUM, FROM 2% TO 10% TUNGSTEN, FROM 4% TO 8% ALUMINUM, FROM 4% TO 8% CHROMIUM, FROM 3% TO 12% TANTALUM, FROM 0.5% TO 2% ZIRCONIUM, FROM .05% TO 1% CARBON, FROM .5% TO 3.5% COLUMBIUM, AND FROM .002% TO .01% BORON. 